Fluid pressure producing device



ATTORNEY.

IVENTOR. Srv/Fr Patented July 14, 1942 .l

Price FLUID PB ESSUBE PBODUCING DEVICE draulierake u i poration of California 'Application November 24, i939, serai No. 306,012

s claims. '(cl. en -54.61'

Thisinvention relates to fluid pressure brak- .e

ing systems, and more particularly to huid pressure producing devices for ,such systems.

Broadly the invention comprehends a. uid pressure producing device having .twoY phases, one for producing low pressure producing a 'relatively high .pressure without 4perceptible increase in the activative force.

An object of the invention is to provide atwophase iluid pressure' producing device including means for distributing thetransition from low to a relatively high pressure over a prolonged and another for4 uperiod so as to smooth out the operation ofthe System. r

Another object of the invention is to provide a twophase fluid vpressure producing device including a low pressure producing means, a high pressure producing means, means for transferring pressure from onewto'the other, and means for inhibiting actuation of the high pressure pr'on ducing means in advance ducing means.

- Otherobjects and'advantages. of the invention ar from the following description taken will `app in connection with the drawing'forming a this specication, and in whichthe invention: Fig. 2 is a vertical sectional view of the fluid pressure producing device;

Fig. 371s `a fragmentary view in section, illuslthrough for ventingithe reservoir to the atmosphere. 'I'he cover plate also hs"thereon a packing box and an opening 22theretl irough con- Y 20 o'f the low pressure proei' part of Fig. 1 is a schematic view of'a iiuid pressure braking system embodying centricauy disposed withy relation to tnefpoorv ing box.

A cylinder Vu depending from the'bottom of 4s" 'the reservoir andfopening into the reservoir in vconcentric relatinto the ,opening '22 in the cover plate"y incfdes a largJeJchaiiber 26 opening directly `into the ,reservoir and communicating .with the reservoir as by a passage 28; and a relatively small chamber 30 arranged in concentric relation to and forward of the large chamber and separated therefrom as by a diaphragm 32 having a concentric opening 34 providing a commu- Harvey C. Swift, Detroit, Mich., assigner to Hy- Company, Detroit, Mich., a corand the small chamber is closed as by a head 38 provided with a discharge port 38.

A fluid pressure delivery pipe or conduit 40 connected to the discharge port 3 8 has branches connected respectively to fluid pressure actuated motors 42, preferably arranged in pairs, one pair for actuating brakes associated with the front wheels of a vehicle, and another pair for actuating brakes associated with the rear wheels of the vehicle.

The brakes may be of conventional type each including a ilxed support pr backing plate 44 adapted to be secured to an axle orto an axle housing, a rotatable drum 46 associated with the backing plate and, adapted to be secured to a wheel, a pairof corresponding interchangeable friction eleme'nts or shoes 48 mounted on the backingplate for cooperation with the drum, a retractile spring 5I "connecting the shoes, and a motor corresponding to the motors 42 mounted on the backing plate between the shoes and operative to actuate the shoes into engagement with the drum against the resistance of the retractile spring 50.

A hollow piston 52 reciprocable in the small chamber 30 has a concentric opening or port 54 in-its head, and se'ated on the head of the piston is a sealing cup 56 having a concentric opening 58. The perimeter of the cup deilning the opening 58 overhangs the perimeter of the head deiining the. opening 54, the object of which will hereinafter appear. A spring 60 interposed between the cup 56 and the head 36 of the small chamber serves to retain the sealing cup 56 against displacement and also to return the piston 52 to its retracted position wherein the piston seats onthe diaphragm 32.

'A piston 62 reciprocablein the large chamber 12E is held against displacement as by a retaining rlngk seated in a groove in .tliehwall of the large chamber a aceiitthat end lof the chamber opening into th reservoir. rThe pistdn 62 includes a- 'a chamber 'I0 closedfasfbya head 12 having a plurality of equally,l aced ports 14 and a concentric boss ,18 provi with a socket 18, the purpose of which will hereinafter appear.

The head Si has a concentric extension projected through the opening 34 in the diaphragm 32 between Athe chambers 26 and 30. The extension 8l has a reduced end portion 82 adapted to enter the opening 54 in the head of the hollow piston 52 and abut the overhanging perimeter of the sealing cup 56 so as to seal the piston 52,andl

nication between the large and small chamber, 55 the extension also'has a plurality of spaced longitudinally extended circumferential grooves or channels 84 normally providing communications between the chamber 26 and the hollow piston The head 66 of the .piston 62 and the extension 80 thereon are axially bored to provide a chamber 86 communicating directly with the hollow piston 52 and the chamber 10, also with the chamber ,26 by way of spaced ports 88. The head 66 has thereon a vsealing cup 90, and a spring 82 sleeved on the extension 80 .between this cup and the diaphragm 32 serves to retain the cup against displacement and also to return the piston to its retracted position. v

A piston 94 reciprocable in the chamber 86'has on its head a sealing cup 96 for inhibiting seepage of fluid past the piston, and on the back of this piston is a. rod 98 supportingl a valve |00 Asuitable -for cooperation with a valve seat on the back of the head 66 of the piston 62 for control of the communication between the chambers 'I0 and 86. The valve has 'a concentric doublediametral extension |02, and sleeved on this extension is a spring |04 supporting a perforated disc |06, also sleeved von the extension, and the disc is supported on a compressible sealing cup |08 having spaced openings ||'0 therethrough registering with the openings 14 of the closure plate or head 12.

A thrust rod I2 extending through the stuiling box 20 and opening 22 in the cover of the reservoir has one of its ends seated in the socket 'I8 on the back of piston 62, and the other end of this rod has an enlarged head |'|4. A foot pedal lever ||6 rockable on a stub shaftv ||8 carries a.

roller |20 for cooperation with the head ||4, and

a retractile spring |22 connects the lever. to a fixed supportA |24.

'In a normal operation, upon depressing the foot pedal lever |6, force is transmitted from the lever through the rod ||2 to the piston 62, result:

ingin advancing the piston on its compression stroke. `During the initial movement of -the piston 62 on its compression stroke, the sealing cup 90 on the head o the piston closes the communication '28 between the reservoir I0 and the chamber 26, and, thereafter, as the piston 62 advarices on its compression stroke, fluid in the chamber 26 forward of the piston 62. is displaced from the rcylinder through the channels 84 into the hollow piston 52, thence through the port 54 in the head of 'tire piston 52 and the opening 58 in the sealing cup'56 into the small chamberv 30,

through the discharge port 38 and fluid pressure delivery pipe 40 and its branches into the motors 42 to further actuate the motors so as to increase the braking force.

During this operation, the iiuidin the chamber 26,-forward of the piston 62 is displaced therefrom through the ports 88 into the chamber 86,

26 should not take place rapidly, because under l such a condition the iirst phase of the operation would be completely lost and pressure on the fluid would be created only in the small chamber 30. V

To avoid such a contingency, during a normal operation, after the attainment of the predetermined pressure on the iluid in the chambers 26 and 30 pressure acting on the plunger 94 and the valve |00 is suiilcient only to .open the valve |00 slowly so that the transition from low pressure to high pressure may be effected smoothly, and the uid in the chamber 26 metered therefrom gradually so as to impose a constantly increasing drag on the piston 52. This is accomplished in view of the increased pressure developed in chamber 30 and the consequent further movement of piston 94 and valve |00 against the resistance of the compressible sealing cup |08 to thereby strangulate the openings ||0 to efect controlled metering of the uid from chamer 26.

In instances where vthe piston 62 is, moved rapidly on its compression stroke, occurring upon an impetuous operation of the brakes, the pressure on the fluid in the chambers 26 and 30, acting on the piston 94 and the valve |00, opens the valve against the resistance of the spring |04 seated on the perforated disc |06 supported on theflexible cup |08 having openings ||0 therethrough registering with the ports 14 in the chamber 10' communicating with the reservoir.

In this operation, during the initial movement oi the piston 62, opening ofthe valve is accomthence through the discharge port 38 and uid f pressure delivery` pipe or conduit "40, and its respective branches into the iiuid pressure actuated motors 42, resulting in energization of the motors and the consequent actuation of the friction velements or shoes 48 into engagement with the drum 46 against the resistance ofthe retractile springs 50 to effectively retard rotation of the drums.

Upon advance of the piston 62 for a predetermined portion of its compression stroke, no movement is transmitted to piston 52. As the reduced end 82 on the extension 8 0 of the piston 62 approaches the prt 54 in i;l1episton 52, the surge of uid under pressure from chamber 26 is sufficient to `force the piston 52 forward, spaced apart from the extension 80, until a predetermined pressure is attained on the uid in the system to thereby transfer thepressure to the piston 52 from the piston 62. With the transfer of pressure to the piston 62, pistons 52 and 62 move asa unit, and the uid in the chamber 30 forward of the piston 62 is displaced therefrom plished quite rapidly, and this results Iin compressingv the flexible cup |08 to such an extent that the openings |0are closed so that the pres-v sure on the fluid in the cylinder 26 is not relieved until a-fbalance of pressure is attained in the chambers 26 and 30 equivalent to .or slightly greater than the predetermined pressure, thereby acting ongthe piston 94 andthe valve |00 as to retain the valve open but not to such an extent l as tovimpose suliicient pressure on the iiexible cup to close the openings ||0, yet adequate to so distort the cup as to restrict the openings lill, to the end that the uid in the chamber'26 may be metered gradually therefrom as the pistons are further advanced.

Upon c onclusion /of a vbraking operation, the foot pedal lever ||6 is released, and is returned toits normal retracted position under the influence of the retractile spring |22.v This results 's in release of the vpiston 62 and return of this piston to its retracted position under the' influence of the retractile spring 02, and return of the piston 62 results in release ofV the piston 52 and return of this piston to its retracted position sage including a valve responsive to pressure on under the iniiuence of the retractile spring l0. `the uid in the cylinder, and a compressible As the piston62 returns to its retracted posimember cooperating with the valve having adiation, the valve 400 closes under the iniluence of tortable orifice therethrough iorthrottling the the spring |04, and the cup 90 on the head of 5 passage upon forward movement of the piston. the piston uncovers the passage 28 providing a 6. A iiiiid Pressure producing deviee impriscommunication between the reservoir and the ings. rervoina cylinder depending therefrom chamber 26. i Also, the-extension 80 on the pisandv opening into the reservoir, a piston recipton 62 is withdrawn from the port 54,111 the head '20681316 in the cylinder having 8' hOllOW bOdy DIO- .of the piston 52 so as tocstablish communica- 10 Viding a Chamber 8 port Opening through tion between the chambers 26 and 30, and during Y the heed 01.'.the Piin and an Opening Provi this operation fluid is returning to the chamber acommunication` between the chamber andthe 3tl-from the fluid pressure actuated motors 42 and reservoir. a valve for control 0i' the P011. and the fluid pressure delivery pipe 4o and branches compressible member having a diswrtable orifice thereof connecting the motors to the cylinder. l5 under the influence of the retractile springs of and theTeSW011 the brake structures. The iluid received in the A iiuid pressure DlOdliCiDE deviee 00111D118- chamber 3s is displaced therefrom, through the ins a reservoir, a cylinder depending from and f port 54, into the hollow piston 52. thence through the passages a4 in the circumference of the ex- 2o in the. cylinder including paced heads each hav-` iensiun so, into the chamber ze, thence through ins an opeliim;v therethroush AI forwardly exthe passage 28 into the reservoir. tended projectlcn 0n 011e .0f the 91890118 liillited While this invention has been `dmrihed in to enter andclose the opening in the other head, connection with certain speciiic embodiments, Said extension havin! B me thrthrlilh the principle involved is susceptible of numerous 25 mii-edm with the openings m the had! 0f the other applications that .will readily occur to perl. PitOnlnd 90m wmmumcunl with the W1- sons skilled in the'a The inventinis, therei index' *tween theihead mi m9033101' mm fore, to be limited only as indicated by the scopeof the passage including a valve and a comof the appended du pressibie member having a distortabie prince i017 VHaving thus described the various features oi 30 mmm them 's lor control oi the opening between .the chamber Y opening into the reservoir. a piston reciprocablg i of the piston.

2.. A fluid pressure producing device compris- 4ing a cylinde a piston movable therein for creat-s the invention, what vI claim as new and desireA to secure by Letters Patent is:

1. A iluid pressure producing device compris-f ing a cylinder. a piston movable therein for creating pressure havinga passage therethrough. and,` 35 `meansv for control of the passage including a compressible member .havinga variable urice-` therethrough operative to throttle the iluid Il ow through the passage upon the initial movement ing pressure. having a passageA therethrough. means for control oi the passage including a valve, and a ilexible cup having a variable oriiice 45' therethrough for coo ration with the valve operative upon the crealie lthe fluid ilow through the passage. i

3. A iluid pressure producing device comprising a cylinder, a piston movable therein-for creat- .50. ing pressure having a passage therethrough, and

means for control of the passage including a valve and a compressible member having a dis, tortable oriilce therethrough operative upon the advance of the piston to incrementlyv meter the u flow of duid through the passage.

4. A iluid pressure producing device comprising .a cylinder depending from a reservoir, a piston movable therein for creating 'pressurefhaving a passage therethrough communicating with .0

the reservoir, a valve responsive to pressure on the iluid in the cylinder normally closing the passage, a'nd compressible means having variable orinces therethrough for throttling the fpassagel c" controlled by the valve upon theforward movement of the piston. 5. 'A fluid pressure producing device comprising a cylinder depending from a reservoir, a pis'- ton movable therein tor creating pressure havfo ing an opening therethrough communicating with the reservoir. means ior control oi the pason of pressure to throttle with the openings in the heads'oi' the pistons and ports `communicatingl with the largechamber. a piston movable in thepassage responsive topressure on the fluid inthe small chamber. a

valve carried by the last-mentioned piston for 'control of the passage, and a-compressible member cooperating with 'the valve having a -distortable oriilce for throttling the time.

9.A iiuidpressure producing device comprising .a reservoir, a cylinder depending from and communicating with the` reservoir having a large cylinder provided with a port commlmicang with the reservoir and a small-chamber having a discharge Port, a piston reciprocable in the large chamber therein provided with a port .op'eningjthrough the head ci the pischamber having a ton andan openingcommunicatin'gwithethe resv ervoir,l a piston reciprpcable in the smallchamber having a port in` its head, an extension on the piston' in. the large chamber adapted to enter chamber; said extension having a passponsive to pressure on thev iluidV in'the small chamber. a valve-carried by the last-mentioned v piston for control ofthe passage,A and compressi-ble member havingjadistortable oriiice for controL-or. the communication between the reservoir and the chamber` inthe piston.

- t HARVEY c. swm'rl and closethe'f-port in the head of the piston in4 sage therethrough communicating with the ports in theheads or the pistons, and a plurality oi 

